Go to Settings > Security > Unknown Sources (or Install from unknown apps on newer Android) and allow your browser or file manager to install APKs.
In most cases, Google Play Services updates automatically in the background. However, users often seek out specific APK versions (like the 13.2.80 series) for several reasons: Legacy Support: Go to Settings > Security > Unknown Sources
If you have 1GB or 2GB of RAM, version 13.2.80 uses approximately 40-60MB in the background, whereas newer versions can exceed 120MB. Go to Settings >